# sinpi, sinpif, sinpil, sinpid32, sinpid64, sinpid128

From cppreference.com
< c‎ | numeric‎ | math

Defined in header ``<math.h>`` |  |
float sinpif( float arg ); | (1) | (since C23)
double sinpi( double arg ); | (2) | (since C23)
long double sinpil( long double arg ); | (3) | (since C23)
_Decimal32 sinpid32( _Decimal32 arg ); | (4) | (since C23)
_Decimal64 sinpid64( _Decimal64 arg ); | (5) | (since C23)
_Decimal128 sinpid128( _Decimal128 arg ); | (6) | (since C23)
Defined in header ``<tgmath.h>`` |  |
#define sinpi( arg ) | (7) | (since C23)

1-6) Computes the sine of `π·arg` measured in radians, thus regarding arg as a measurement in half-revolutions.
7) Type-generic macro: calls the correct function based on the type of arg. If the argument has integer type, (2) is called.

The functions (4-6) are declared if and only if the implementation predefines `__STDC_IEC_60559_DFP__` (i.e. the implementation supports decimal floating-point numbers). | (since C23)

### Parameters

arg | - | floating-point value whose product with `π` represents an angle in radians

### Return value

If no errors occur, the sine of `π·arg` (sin(π×arg)) in the range [-1, +1], is returned.

### Error handling

Errors are reported as specified in `math_errhandling`.

If the implementation supports IEEE floating-point arithmetic (IEC 60559):

- if the argument is ±0, it is returned unmodified;
- if the argument is ±∞, NaN is returned and FE_INVALID is raised;
- if the argument is NaN, NaN is returned.

### Example

Run this code

    #include <errno.h>
    #include <fenv.h>
    #include <math.h>
    #include <stdio.h>

    #ifndef __GNUC__
    #pragma STDC FENV_ACCESS ON
    #endif

    #if __STDC_VERSION__ < 202311L
    // A naive implementation of a subset of sinpi family
    double sinpi(double arg)
    {
        return sin(arg * (double)3.1415926535897932384626433);
    }
    #endif

    int main(void)
    {
        const double pi = acos(-1);

        // typical usage
        printf("sinpi(1) = %f, sin(pi) = %f\n", sinpi(1), sin(pi));
        printf("sinpi(0.5) = %f, sin(pi/2) = %f\n", sinpi(0.5), sin(pi / 2));
        printf("sinpi(-0.75) = %f, sin(-3*pi/4) = %f\n", sinpi(-0.75), sin(-3 * pi / 4));

        // special values
        printf("sinpi(+0) = %f\n", sinpi(0.0));
        printf("sinpi(-0) = %f\n", sinpi(-0.0));

        // error handling
        feclearexcept(FE_ALL_EXCEPT);
        printf("sinpi(INFINITY) = %f\n", sinpi(INFINITY));
        if (fetestexcept(FE_INVALID))
            puts("    FE_INVALID raised");
    }

Possible output:

    sinpi(1) = 0.000000, sin(pi) = 0.000000
    sinpi(0.5) = 1.000000, sin(pi/2) = 1.000000
    sinpi(-0.75) = -0.707107, sin(-3*pi/4) = -0.707107
    sinpi(+0) = 0.000000
    sinpi(-0) = -0.000000
    sinpi(INFINITY) = -nan
        FE_INVALID raised

### References

- C23 standard (ISO/IEC 9899:2024):

  - 7.12.4.13 The sinpi functions (p: 247-248)

  - 7.27 Type generic math <tgmath.h> (p: 387)

### See also

sinsinfsinl (C99)(C99) | computes sine (\({\small\sin{x} }\)sin(x)) (function)

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